1. Field
This disclosure relates generally to communication systems and, more specifically, to detecting orthogonal frequency-division multiplexing and discrete multi-tone symbols, that are repeated multiple times by concatenating multiple copies of a unique orthogonal frequency-division multiplexing or discrete multi-tone symbol end-to-end without using cyclic prefixes, by using over-sized discrete Fourier transforms.
2. Related Art
Orthogonal frequency-division multiplexing (OFDM) refers to an approach to encode digital data on multiple carrier frequencies. OFDM, which may be deployed in wireless or wired applications, has become a popular technology for digital communication systems. OFDM is employed in a wide variety of applications, e.g., digital television and digital audio broadcasting, digital subscriber line (DSL) broadband Internet access, and fourth generation (4G) mobile communications. OFDM modulation is similar to discrete multi-tone (DMT) modulation and employs frequency-division multiplexing (FDM) as a digital multi-carrier modulation process.
In OFDM, a number of closely spaced orthogonal subcarriers are used to carry data on several channels in parallel. Each subcarrier is modulated with a conventional modulation scheme (e.g., quadrature amplitude modulation (QAM) and phase-shift keying (PSK)) at a relatively low symbol rate, while maintaining total data rates similar to conventional single-carrier modulation schemes that utilize a similar bandwidth. A primary advantage of OFDM implementations over single-carrier approaches is the ability of OFDM to cope with severe channel conditions (e.g., attenuation of high frequencies in a copper conductor, narrowband interferences, and frequency-selective fading due to multi-path interference) without implementing complex equalization filters.
Power-line communication (PLC) refers to transmitting data on an electrical conductor that is also used simultaneously for alternating current (AC) electric power transmission to consumers. A wide range of PLC technologies may be deployed for different applications, ranging from home automation to Internet access. Most PLC technologies are limited to premises wiring within a single building or a distribution network wiring, but some PLC technologies can be implemented in both distribution network wiring and premises wiring. Typically, multiple PLC technologies are required to form relatively large networks. PLC technologies may provide different data rates and utilize different frequencies for different applications.
Several PLC channels may be coupled onto one high-voltage (HV) line. Filtering devices are usually applied at substations to prevent the carrier frequency current from being bypassed through the station apparatus and to ensure that distant faults do not affect the isolated segments of a PLC system. Narrowband PLC works at frequencies from 3-500 kHz, data rates up to 100s of kbps, and has a range up to several kilometers which can be extended using repeaters. Broadband PLC works at higher frequencies (1.8-250 MHz), higher data rates (up to 100s of Mbps) and is used in shorter-range applications. Recently, narrowband PLC has been receiving widespread attention due to its applications in the Smart Grid. Narrowband PLC has also been used in smart energy generation, particularly in micro-inverters for solar panels. Narrowband PLC standards include G3-PLC (36-90.6 kHZ), PRIME (42-89 kHZ), IEEE 1901.2 (9-500 kHZ), ANSI/EIA 709.1, .2 (86 kHz, 131 kHZ), KNX (125-140 kHZ), and IEC61334 (CENELEC-A). Broadband PLC, in contrast, has mainly found acceptance as a last-mile solution for Internet distribution and home networking. With high data rates and no additional wiring, broadband PLC is seen as an effective technology for multimedia distribution within homes.
In general, smart meters are configured to gather data for remote reporting to a central station using two-way communication. In a typical installation, a smart meter may communicate with a central station over a power-line using a differential demodulation technique with forward-error correction (FEC). The term ‘smart meter’ may be used to refer to various devices that measure utilities, such as electricity, natural gas, and water consumption. Smart meters usually implement real-time or near real-time sensors and may facilitate power outage notification. Smart meters may also facilitate measuring site-specific information, allowing price setting agencies to introduce different prices for consumption based on the time of day and the season. Smart meters may also measure surge voltages and harmonic distortion, allowing diagnosis of power quality problems.
Smart meters generally help consumers better manage their energy use based on up-to-date information on gas, water, and electricity consumption and in doing so help people reduce energy bills and carbon emissions. Electricity pricing usually peaks at certain predictable times of the day and the season. In particular, if generation is constrained, prices can rise if power from other jurisdictions or more costly generation is brought online. Implementing smart meters allows consumers to adjust their consumption habits to be more responsive to market prices, which may delay the construction of additional generation or at least the purchase of energy from higher priced sources.